1. Field of the Invention
The invention relates to a nut, more particularly to a nut with a threaded blind hole for use on a printed circuit board.
2. Description of the Related Art
Currently, to solder circuit-related components on a printed circuit board (PCB), each component is sucked by a suction nozzle first, and is then released to a predetermined position on the PCB. After all the components are mounted on the PCB, the latter is heated by passing through a soldering furnace, thereby soldering all components on the PCB.
Referring to FIG. 1, a conventional nut 3 includes an annular surrounding wall 31 and a through hole 32 defined by the annular surrounding wall 31. Since a suction nozzle 5 cannot apply a negative pressure to the nut 3 due to the presence of the through hole 32, a soft top plug 33 has to be mounted on a top surface 34 of the nut 3. The top plug 33 includes a head portion 332, and a shank portion 331 that extends into the through hole 32 and that has an outside diameter slightly larger than the inner diameter of the through hole 32 such that the shank portion 331 forms an air-tight seal with the through hole 32, thereby sealing the through hole 32.
During assembly, the suction nozzle 5 applies a negative pressure to the head portion 332 of the plug 33 so as to hold the nut 3, and subsequently releases the nut 3 to a predetermined position on the PCB 4. The PCB 4 is then passed through a soldering furnace (not shown) so that the nut 3 and the other components are soldered on the PCB 4. The plug 33 is removed after assembly. When an automated arm (not shown) is used to remove the plug 33 from the nut 3, it is likely that the connection between the nut 3 and the circuit board 4 is damaged. As such, manual removal is needed.
Referring to FIG. 2, a cap 33′ can be mounted on the top surface of the nut 3 instead of the plug 33 (see FIG. 1) to cover the through hole 32. The cap 33′ has a clamp portion 331′ with an inner diameter slightly smaller than the outer diameter of the nut 3, such that the clamp portion 331′ can be sleeved tightly on the surrounding wall 31 of the nut 3. The cap 3′ is also manually removed from the nut 3 after the nut 3 is soldered on the PCB 4.
Since the through hole 32 in the conventional nut 3 has to be covered by the plug 331 or the cap 331′ before soldering on the PCB 4, and since the plug 331 or the cap 331′ has to be manually removed after soldering on the PCB 4, the assembly steps and the assembly cost for mounting the conventional nut 3 on the PCB 4 are increased.